New trout stocking policy approved

New trout stocking policy approved

Dec. 21, 2000

DENVER — The Colorado Wildlife Commission has approved a new policy that will end the stocking of fish exposed to the whirling disease parasite in any lakes or streams where trout may reproduce by 2003.

The Commission policy, adopted Nov. 16, directs Division of Wildlife aquatic managers to limit the stocking of exposed fish to lower elevation lakes and reservoirs that are not near habitat where trout can reproduce. This includes such waters as Cherry Creek Reservoir in Denver, Highline Reservoir in Grand Junction and Prospect Lake in Colorado Springs. Division biologists recommended that the policy be adopted.

Commission policy already prohibits the stocking of fish from positive hatcheries into any lakes or streams free of the whirling disease parasite. Stocking of positive fish into waters that already contain the parasite has continued because there was no evidence the stocking, which provided fishing for thousands of anglers, increased the risk of spreading the parasite to negative waters.

But new research conducted by the division over the past two years strongly suggests that continued stocking of positive fish into positive waters increases the level of infection in such waters. And DOW wild trout researcher Barry Nehring has found that brook trout populations have been reduced and in some cases eliminated in streams below some reservoirs that have been regularly stocked with infected fish.

"Based on that research, we concluded that it’s appropriate to eliminate stocking of positive fish in trout waters, even those where the parasite is already well established," said Eddie Kochman, the DOW’s aquatic wildlife manager. "Long-term protection of Colorado’s fishery resource is the first priority, and current research strongly suggests that continued stocking of whirling disease positive fish is a threat to that resource."

The division is continuing its successful effort to rid key hatcheries of the whirling disease parasite to increase the production of negative-testing fish. The Finger Rock Rearing Unit near Yampa is the most recent facility to gain negative status under Wildlife Commission regulations. Other hatcheries already successfully renovated and free of the whirling disease parasite include Bellvue, Buena Vista, Mt. Ouray, Durango, Salida’s isolation unit and the agency’s research hatchery near Fort Collins. The Pueblo, Crystal River and Glenwood Springs rearing units have remained negative.

Work is continuing on the Roaring Judy, Rifle Falls and Mt. Shavano facilities, three of the state’s biggest fish rearing units. The Division also plans to renovate the smaller Pitkin Rearing Unit. Hatchery managers hope to have all four free of the parasite within the next two years.

In addition, the DOW is now evaluating whether to build new hatcheries and buy more negative fish from private trout growers.

Whirling disease is a parasitic infection that attacks the nervous system and cartilage of young trout. Older fish can carry the parasite but are much less likely to be severely impacted by whirling disease. Newly hatched trout, particularly rainbows and some strains of cutthroats, can be infected to the point where they seldom survive to their second year.

Other species, including brown and lake trout and some subspecies of cutthroat trout and kokanee salmon either survive or avoid infection entirely.

"The division is looking to a future where we can once again produce and stock enough disease-free fish to provide the fishing recreation that we did before whirling disease," said Eric Hughes, the division’s statewide hatchery manager.

"We will continue both our hatchery renovation and research, including management techniques that may reduce the impact of whirling disease in some streams," Kochman said.